Optimal two-iteration sculling compensation mathematical framework for SINS velocity updating

A new two-iteration sculling compensation mathematical framework is provided for modern-day strapdown inertial navigation system（SINS） algorithm design that utilizes a new concept in velocity updating. The principal structure of this framework includes twice sculling compensation procedure using incremental outputs from the inertial system sensors during the velocity updating interval. Then, the moderate algorithm is designed to update the velocity parameter. The analysis is conducted in the condition of sculling motion which indicates that the new mathematical framework error which is smaller than the conventional ones by at least two orders is far superior. Therefore, a summary is given for SINS software which can be designed with the new mathematical framework in velocity updating.

Propulsion Principles of Water Striders in Sculling Forward through Shadow Method

Semi-aquatic arthropods skate on water surfaces with synergetic actions of their legs. The sculling forward locomotion of water striders was observed and analyzed in situ to understand and reproduce the abovementioned feature. The bright-edged elliptical shadows of the six legs of a water strider were recorded to derive the supporting force distributions on legs. The propulsion principles of water striders were quantitatively disclosed. A typical sculling forward process was accomplished within approximately 0.15 s. Water striders lifted their heads slightly and supported their weight mainly by the two driving legs to increase the propulsion force and reduce the water resistance during the process. The normalized thrust-area ratio （defined as the ratio of the propulsion force to the projected area） was usually lower than 0.4 after sculling for approximately 0.08 s. The entire normal supporting force remained nearly constant during a stroke to reduce the mass center fluctuation in the normal direction. In addition, water striders could easily control the locomotion direction and speed through the light swinging of the two hind legs as rudders. These sculling principles might inspire sophisticated biomimetic wa- ter-walking robots with high propulsion efficiency in the future.

Low Friction Traction for Cervical Spine Dislocation

In order to reduce the magnitude of the force applied to skull for treatment of acute cervical spine dislocation, we developed a method of skeletal traction based on reduction of friction forces under the patient’s head. Traction force was applied to sculls of five patients with cervical fracture-dislocations. A difference in friction interface between the patient’s head and shoulder girdle was created. The traction weight required for the reduction of the vertebral dislocation was significantly lower than an expected minimal traction weight in the commonly used techniques (p = 0.013). The presented method permits an effective and safe reduction of dislocated cervical vertebra by a relatively low traction force.